Making a fabric rainproof is relatively easy, but making them waterproof is not at all.
Waterproof fabrics are fabrics that are inherently, or have been treated to be resistant to water and wetting, and suitable for many different uses.
They are natural or synthetic fabrics, laminated to or coated with a waterproofing material like rubber, polyurethane (PU) and polyvinyl chloride (PVC), silicone elastomer, fluoropolymers and wax.
Waterproof/breathable fabrics resist liquid water to go through, but allow water vapour to do so. Their ability to block out wind, rain and snow and at the same time and to allowe vapour from sweat to evaporate explains their use in rainwear, waterproof outdoor sports clothing, tents, and other applications.
Nowadays there are essentially four types of waterproof breathable fabric regularly used in the outdoors: tightly woven fabrics, fabrics with microporous coatings or membranes, fabrics with a continuous hydrophilic coating or membrane and bicomponent microporous and hydrophilic laminates. Besides, some garments are considered to be weatherproof – without being technically waterproof.
The performance of these fabrics depend on their laboratory tests. Water resistance is measured by the amount of water (in mm), which can be suspended above the fabric before the water seeps through. Breathability, or in better terms moisture vapour permeability (MVP) or moisture vapour transmission (MVT) means that the fabric transports water vapour from the body.
Recently, sporting goods manufacturers strated to include this information on their product labels. Mid-range materials usually have values of 5,000 mm of water resistance and 5,000 g of breathability; the best fabrics have 20,000 mm and 20,000 g.
|Waterproof Rating (mm)||Resistance provided||What it can withstand|
|0-5,000 mm||No resistance to some resistance to moisture||Light rain, dry snow, no pressure|
|6,000-10,000 mm||Rainproof and waterproof under light pressure||Light rain, average snow, light pressure|
|11,000-15,000 mm||Rainproof and waterproof except under high pressure||Moderate rain, average snow, light pressure|
|16,000-20,000 mm||Rainproof and waterproof under high pressure||Heavy rain, wet snow, some pressure|
|20,000 mm+||Rainproof and waterproof under very high pressure||Heavy rain, wet snow, high pressure|